Hey Glort,
This 3P setup will be for grid tie in, not independent operation. I foresee that I might tie in a phase on the 3 phase to the alternator to do independent stuff... The alt will do the frequency and basic V regulation and the 3 phase would be in an "assisting" role, hence the 10% up on the speed of the 3P vs the Alt... If I find it too much and there is a bit of breakdown of the flux(Too much mag slip) in the 3p I can just drop the revs a bit by machining the drive pulley down a bit (the one on the alt shaft)...
I have played a bit with induction gens, they are sometimes always "tricky" to set up where voltage surge due to variable loads occur, but much easier in the role of tied in rather than stand alone. Stand alone requires a much more touchy setup of L-C network vs load vs revs to get things working, change but a small amount and things get interesting indeed.... I must confess though, I have not "hard belted" an alt to a 3P in a fixed ratio environment before, and am keen to see if they can be made to work in harmony... I don't see why not... This could end up being an easy (and cheap) way to boost say a 5kva to a 10kva unit by adding an induction generator into the mix....
10% up is around the max you could drive an induction generator in assisting mode if I remember correctly, the performance is already starting to fall off at this point, the actual real efficiency is around 4 or 5% up for coupling... To determine it by looking at the motor plate, look at the rated revs for the power. ie 1440rpm in this case - this is then a 2 pole set motor @ 50hz - the 60rpm deficiency is the "slip" required on the rotor to give rated power at shaft - if you work it out, this is a 100-(1440/1500x100)%=4% slip to induce current in the rotor to give grunt at the shaft... To get the same amount of current(or near enough) boost back into a tie in system, you would have to drive the shaft at 4% above 1500RPM ie 1560... But enough said, lets try it and see! What I am actually hoping to achieve, is less electrical load on the gen head as part of the trial... If it doesn't work to my liking, no biggie, I will just run them independently...(or the 3 phase not at all, 4 bolts and a belt and it disappears back into storage!!)
As an aside, have you ever run a 3P motor as a rotary phase converter from 1P mains? I have a couple set up to use where 3 phase polishing machines (crappy bench grinder with buffing wheels) were needed... start the "rotary transformer" with a cap, once spinning, hook up the 3P grinder to the 3 phases on the "converter", and away it goes.... Much cheaper and more reliable than the inverter controllers (if you don't need speed control)... Plus, 3P industrial motors are a dime-a-dozen at the scrappies.... Singles are in way more demand and difficult to get, when you do, you bleed money to cover them... Just bear in mind, you are only getting about 1/3 the rated 3phase power out of the converter this way - so a 15kw 3phase will only give you around 5kw 3phase out to power another device (approximately)...oh, and BTW, you need 220V 3phase motors to make it work with reasonable power output...
Yesterday evening I did the line up of all the pulleys and sub frame for the genhead on TM2 - I gotta work a lot more carefully now that the plasma is down.... no more quick tack, oops, cut move tack... Tack and weld once all lined up only!! I have managed to get the whole shebang together, allowing for dual ratios on the engine/alt coupling, with only the change of the alt pulley - there is enough tension adjustment that I don't have to change belts even - Bonus!! The clearance between the 3P pulley/shaft and the crankshaft necessitated a bit of surgery with an angle grinder, but one stubby 3P motor shaft later, and the conversion from 2 to 1 sheave on the 3P pulley, and all is good to go with enough clearance....Just!! The drive train belt layout is almost an inverted "V" with the crankshaft and 3P at the bottom, almost in line with one another and the genhead shaft above them in the center... Looks quite cute!! I looks like I will be able to drive the water pump from the second sheave (now unused) of the pulley that is on the genhead shaft... an added bonus of the current layout.
Right... Enough rambling....
Keep it spinning
Cheers
Ed